(a) Where a person has made statements under oath which are inconsistent to the degree that one of them is necessarily false, each having been made within the jurisdiction of this state and within the period of the statute of limitations, the prosecution may proceed by setting forth the inconsistent statements in a single count alleging in the alternative that one or the other was false and not believed by the defendant to have been true when made. In such case, it shall not be necessary for the prosecution to prove which statement was false, but only that one or the other was false and not believed by the defendant to be true.
(b) The highest degree of perjury of which the defendant may be convicted shall be determined by hypothetically assuming each statement to be false and perjurious. If perjury of the same degree would be established by the making of each statement, the accused may be convicted of that degree at most. If perjury of different degrees would be established by the making of the two statements, the accused may be convicted of the lesser degree at most.